Outside of windows, you’ve essentially described my radionale for building a PC. I was planning to build a Linux machine to 1. Save on not having to buy windows and 2. Simply because I like Linux, and (besides competitive games) gaming on Linux seems to be a pretty solid option nowadays. I wanted to buy second hand as much as I could and upgrade piecemeal to keep up with hardware demands and improve my experience.
The convenience of the steam deck is attractive because I’ve never built a machine before and graphics aren’t all that important to me. But I do like the prospect of having something that will last and be able to be iteratively improved for years to come